MAPLE SIRUP PRODUCERS MANUAL 



91 



PN-479H 



Figure 102. — Sirup being packaged in lithographed cans. 



Stack BiiiTi 



If packaged sirup is stacked while it is still 

 hot, the same browning reaction that occurred 

 in the evaporator will continue and darken the 

 sirup by as much as one or two grades. This 

 seldom occurs with fancy grades of sirup. De- 

 velopment of color in hot packaged sirup is 

 called stack bum. To prevent stack bum, the 

 containers should be temporarily stacked with 

 an air space to allow air to circulate, and a fan 

 should be used to speed up cooling. After the 

 cans have cooled to room temperature, they can 

 be close packed. 



Control of \Iiero-Org;anisins 



Standard-density sirup will not support ac- 

 tive growth of micro-organisms with the excep- 

 tion of a few types of yeast and one or two types 

 of bacteria. Because of the possible contamina- 

 tion of sirup with these organisms, sirup that is 

 offered for sale to the consumer should be 

 packaged hot. The sirup must be heated to at 

 least 180° F. and then packaged immediately 

 (27). 



Everyone has seen mold growing on sirup. 

 However, mold will not grow in standard-den- 

 sity sirup. These apparently contradictory 

 statements are explained as follows: Cold- 

 packed maple sirup may contain mold spores. 

 The mold spores, like the spores of most yeast 

 and bacteria, will remain in a resting state and 

 will not germinate as long as all the sirup is of 

 standard density. 



Sirup stored under ordinary conditions usu- 

 ally undergoes some temperature change. 

 When the storage temperature increases, some 

 of the water of the sirup is distilled up into the 

 head space of the container. When the storage 

 temperature decreases, this vapor condenses 

 into small drops of water that run down onto 

 the surface of the sirup and produce a layer of 

 low-density sirup in which mold and other types 

 of spores can vegetate and grow. 



Even though the sirup contains spores, their 

 growth can be prevented by momentarily in- 

 verting the packaged sirup once or twice 

 weekly (7J^). This destroys the layer of dilute 

 sirup and thus inhibits germination of the mold 

 spores. 



Although sirup is packaged under clean, sani- 

 tary conditions, this does not guarantee that 

 the sirup will not become inoculated with micro- 

 organisms if it is packaged cold. Once mold or 

 yeast has grown in the area where cold packag- 

 ing is done, it is almost impossible to package 

 sirup by the cold method without its becoming 

 infected. 



Chemical inhibitors have long been used for 

 preserving foods. Studies (30) have shown that 

 one of these, the sodium salt of propyl parahy- 

 droxybenzoate (PHBA), is effective in control- 

 ling growth of yeast and mold in maple sirup. A 

 concentration of only 0.02 percent is required. 

 Sodium propyl PHBA is available commercially 

 under different trade names. 



